Pointers
NmpRmpHand locates the RMP handle that contains the selector for the NPN RMP segment.
NPN field npn_link points to the double linked list of NP structures that are instances of the named pipe.
Instances of named pipes are double-lined by np_flink and np_blink.
NP fields np_selector1 and np_selector2 point to associated NPB structures.
The NP is allocated from the system arena.
The NPB is allocated from the kernel resident heap.
NPN owner id is npipenpn (0xff30).
NPB owner id is npipenbuf (0xff9f).
There are four important data structures associated with named pipes: the SFT corresponding to an open named pipe, a pair of kernel internal data structures describing the pipe and one or two allocated memory segments which contain the data buffers for the pipe.
The parts of the SFT specific to named pipes are:
sf_flags SF_NMPIPE and SF_PIPE set
sf_np pointer to pipe info.
sf_pipmod mode of pipe, per-sft internal state bits
Where:
sf_np is defined to be sf_fsd+0, the pointer to np structure
sf_pipmod is defined to be sf_fsd+4, the mode of pipe, plus internal state
NP Named Pipe data structure
The internal data structure for an instance of a pipe. One of these structures is allocated for each open instance of a particular named pipe.
Allocated NP structures are placed on two lists. The first is headed by ActiveNPList, with list pointer np_next linking together all currently active NP structures.
The second list is headed by the NPN structure defined below and is doubly-linked by the np_flink and np_blink pointers. This list is used to iterate over all instances of a particular pipe name.
旼컴컴컴컴컴컴컴컴쩡컴컴컫컴컴컴쩡컴컫컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� �Field Name �Offset�Length�Type�Description � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻p_state �+0 �1 쿍 퀂tate of pipe � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻p_refcnt �+1 �1 쿍 쿞FT reference count for pipe (1 or 2) � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻p_next �+2 �2 쿥 쿾ointer to next in active list � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻p_flink �+4 �2 쿥 쿾ointer to next instance of pipe � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻p_blink �+6 �2 쿥 쿾ointer to previous instance of pipe � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻p_namkey �+8 �2 쿥 쿝MP key value for npn structure � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻p_scnt �+a �1 쿍 쿬ount of servers (max. 1) � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻p_ccnt �+b �1 쿍 쿬ount of clients (max. 1) � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻p_selector1 �+c �2 쿥 퀂elector for outgoing data buffer � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻p_selector2 �+e �2 쿥 퀂elector for incoming data buffer � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻p_pipmod �+10 �2 쿥 쿾ipe mode specified at creation time � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻p_flags �+12 �2 쿥 쿾ipe flags � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻p_ssft �+14 �4 쿏 쿫ack pointer to server SFT � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻p_csft �+18 �4 쿏 쿫ack pointer to client SFT � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻p_timeo �+1c �4 쿏 쿭efault timeout for DosWaitNmPipe � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻p_ssem �+20 �4 쿏 퀂erver end system semaphore � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻p_ssemkey �+24 �2 쿥 퀂erver's semaphore key � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻p_csem �+26 �4 쿏 쿬lient end system semaphore � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻p_csemkey �+2a �2 쿥 쿬lient's semaphore key � 읕컴컴컴컴컴컴컴컴좔컴컴컨컴컴컴좔컴컨컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴�
NPN Named Pipe Name data structure
The following structure contains the common name for the multiple instances of a pipe. Its key value is used as the ProcBlock key for waiters on the pipe. The key value is also used as an RMP key to look up the name record from the NP structure.
旼컴컴컴컴컴컴컴컴쩡컴컴컫컴컴컴쩡컴컫컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� �Field Name �Offset�Length�Type�Description � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻pn_link �+0 �4 쿏 쿾ointer to first instance � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻pn_key �+4 �2 쿥 퀅nique serial number of name � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻pn_len �+6 �2 쿥 �total length of structure � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻pn_name �+8 �254 쿌 쿻ame of pipe, null terminated � 읕컴컴컴컴컴컴컴컴좔컴컴컨컴컴컴좔컴컨컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴�
NPB Named Pipe Buffer data structure
The following variables are used to control the access to a pipe buffer and are part of the allocated buffer for the pipe. In the case of a duplex pipe, two independent data buffers are allocated. Only one buffer will be allocated for a simplex pipe.
旼컴컴컴컴컴컴컴컴쩡컴컴컫컴컴컴쩡컴컫컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� �Field Name �Offset�Length�Type�Description � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻pb_selector �+0 �2 쿥 퀂elector of buffer � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻pb_first �+2 �2 쿥 쿫ase of buffer � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻pb_in �+4 �2 쿥 쿻ext free byte in buffer � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻pb_out �+6 �2 쿥 쿻ext byte of data in buffer � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻pb_last �+8 �2 쿥 쿮nd+1 of buffer � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻pb_rdlck �+a �2 쿥 퀁ead lock sem. � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻pb_wtlck �+c �2 쿥 퀇rite lock sem. � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻pb_rdsem �+e �2 쿥 퀁ead sync sem. � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻pb_wtsem �+10 �2 쿥 퀇rite sync sem. � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻pb_rdcnt �+12 �1 쿍 쿬ount of readers of buffer � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻pb_wtcnt �+13 �1 쿍 쿬ount of writers to buffer � 쳐컴컴컴컴컴컴컴컴탠컴컴컵컴컴컴탠컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿻pb_data �+14 �2 쿥 퀂ize of data left in pipe � 읕컴컴컴컴컴컴컴컴좔컴컴컨컴컴컴좔컴컨컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴�
np_state allowable values for named pipe state
Internally, byte stream mode pipes store just a collection of bytes in the data buffer. Message stream mode pipes have individual messages preceeded by a word which indicates the size of the message.
Named pipes may be in one of several states depending on the actions that have been taken on it by the server end and client end. The following state/action table summarizes the valid state transitions:
Current state Action Next state
<none> server MakeNmPipe DISCONNECTED
DISCONNECTED server connect LISTENING
LISTENING client open CONNECTED
CONNECTED server disconn DISCONNECTED
CONNECTED client close CLOSING
CLOSING server disconn DISCONNECTED
CONNECTED server close CLOSING
<any other> server close <pipe deallocated>
A special internal state, LISTEN2 is used when a client open is in progress (since some operations may block). This is treated the same as the LISTENING state except that a new open or wait will not recognize it as an available pipe.
If a server disconnects his end of the pipe, the client end will enter a special state in which any future operations (except close) on the file descriptor associated with the pipe will return an error.
旼컴컴컴컴컴컴컴컴컴컫컴컴컴컴쩡컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴커 쿙ame 쿍it Mask쿏escription � 쳐컴컴컴컴컴컴컴컴컴컵컴컴컴컴탠컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴캑 쿙P_DISCONNECTED �1 쿪fter pipe creation or Disconnect � 쳐컴컴컴컴컴컴컴컴컴컵컴컴컴컴탠컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴캑 쿙P_LISTENING �2 쿪fter DosNmPipeConnect � 쳐컴컴컴컴컴컴컴컴컴컵컴컴컴컴탠컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴캑 쿙P_CONNECTED �3 쿪fter Client open � 쳐컴컴컴컴컴컴컴컴컴컵컴컴컴컴탠컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴캑 쿙P_CLOSING �4 쿪fter Client close � 쳐컴컴컴컴컴컴컴컴컴컵컴컴컴컴탠컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴캑 쿙P_LISTEN2 �0x12 쿶nternal; client open in progress � 읕컴컴컴컴컴컴컴컴컴컨컴컴컴컴좔컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴켸
np_pipmod, sf_pipmod bit mask values:
旼컴컴컴컴컴컴컴컴컴컫컴컴컴컴쩡컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴커 쿙ame 쿍it Mask쿏escription � 쳐컴컴컴컴컴컴컴컴컴컵컴컴컴컴탠컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴캑 쿙P_NBLK �0x8000 쿻on-blocking read/write � 쳐컴컴컴컴컴컴컴컴컴컵컴컴컴컴탠컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴캑 쿙P_NBLKR �0x8000 쿻on-blocking read � 쳐컴컴컴컴컴컴컴컴컴컵컴컴컴컴탠컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴캑 쿙P_NBLKW �0x8000 쿻on-blocking write � 쳐컴컴컴컴컴컴컴컴컴컵컴컴컴컴탠컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴캑 쿙P_SERVER �0x4000 퀂et if server end � 쳐컴컴컴컴컴컴컴컴컴컵컴컴컴컴탠컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴캑 쿙P_WMESG �0x0400 퀇rite messages � 쳐컴컴컴컴컴컴컴컴컴컵컴컴컴컴탠컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴캑 쿙P_RMESG �0x0100 퀁ead as messages � 쳐컴컴컴컴컴컴컴컴컴컵컴컴컴컴탠컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴캑 쿙P_TIMOUT �0x3800 �Timeout np_sem_blk & np_sem_wait � 읕컴컴컴컴컴컴컴컴컴컨컴컴컴컴좔컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴켸